Pregnancy Doesn't Actually Make Women Dumber

“Oh my gosh, I think my brain is permanently shrunk after having three kids,” CBS Early Show host Hannah Storm once said. In a diary for New Statesman, Sarah Montague, who co-hosts the BBC’s flagship Today news program, said: “My biggest worry has been what you might call ‘preg-head.’”

Storm and Montague believe they were suffering from a kind of mental impairment brought on by the biological changes associated with pregnancy — an idea that’s been called preghead, pregnesia, momnesia and baby-brain. Anecdotal evidence for the condition is everywhere and frequently shared by writers and broadcasters. The idea has even been endorsed by respected health authorities in the UK. An NHS pamphlet published in 2005 on “50 things would-be fathers should know,” put it this way: “Pregnant women are a bit vague … it’s their hormones.”

Surveys suggest that belief in pregnesia is widespread among the public. In 2008, Ros Crawley at the University of Sunderland quizzed dozens of pregnant and non-pregnant women and their partners, and found that they all agreed that pregnancy is typically associated with cognitive decline.

Given these views, perhaps it’s no wonder that researchers have uncovered disconcerting evidence about the prejudice shown toward pregnant women, especially in work contexts. Although such prejudice is driven by multiple factors, widespread belief in baby-brain likely plays an important part. Consider a study published in 1990, in which Sarah Corse at the University of Pennsylvania invited male and female MBA students to interact with a female manager they’d never met before, and then rate her afterward. In fact, the “manager” was a research assistant acting the part, and the key finding was that students given the additional information that the woman was pregnant reported finding their interaction with her less satisfying than students not fed this lie.

Recently, a spate of human studies has been published that may be hinting at these maternal advantages. For instance, James Swain’s lab at the University of Michigan has shown how several areas in the brains of new mothers are especially responsive to the sound of their own baby crying, compared with the sound of other babies’ cries. Regarding physical brain changes, a team led by Pilyoung Kim at Cornell University and Yale University School of Medicine scanned the brains of 19 new mothers in the weeks immediately after giving birth, and then again several months later. The later scan showed increased volume in a raft of brain areas that are likely to be involved in mothering activities — the prefrontal cortex, parietal lobes, hypothalamus, substantia nigra, and amygdala.